MnSOD plays an important role in protecting cells from injury due to oxidative stress, and is essential for aerobic life. MnSOD catalyzes the conversion of superoxide (O2−) to hydrogen peroxide (H2O2). In eukaryotes, MnSOD is a nuclear-encoded protein that scavenges superoxide radicals in the mitochondrial matrix. Most eukaryotic MnSOD polypeptides are homotetramers and have a total molecular weight of about 88 kDa. MnSOD polypeptides are highly conserved and exhibit around 40% sequence homology among human, yeast, E. coli, and B. stearothemophilus. 